1. Field of the Invention
The present invention relates to an endoscope apparatus having a distal end optical adapter connected to an endoscope with a built-in solid state imaging device.
2. Related Art Statement
In recent years, endoscopes which are capable of observing internal organs in the body cavity and performing several kinds of treatment using treatment tools inserted into treatment tool channels as the need arises by inserting an elongated insertion tube into the body cavity have been extensively used. These endoscopes are used not only in medical treatment but also applied to industrial use for observing and inspecting tubes in boilers, machines and chemical plant, or an internal engine.
In the endoscopes which are used as mentioned above, an electronic endoscope is included. In the electronic endoscope, a solid state imaging device, such as a charge coupled device (written as CCD in the following) is disposed at the distal end of an insertion tube, and an endoscope image formed on the imaging device is displayed on a monitor screen for observation.
Some of the electronic endoscopes for medical use are stereoscopic endoscopes which form an image acquired by each of two objective optical systems on a CCD built in an endoscope insertion tube so as to be capable of observing the image stereoscopically. The stereoscopic endoscopes are indicated in Japanese Patent Application Laid Open No. 64-26813/1989 and U.S. Pat. No. 5,122,650.
Further, in Japanese Patent Application Laid Open No. H1-197716/1989, two objective optical systems having different magnification are disposed and an image obtained by each objective optical system is formed on a CCD corresponding to each optical system, so that an endoscope for, what is called as telephotographic/wide which can observe two images including an ordinary observation image and a magnified image is shown.
On the other hand, in an electronic endoscope for industrial use, a distal end optical adapter type has been known in the art. In the distal end optical adapter, various kinds of objective optical systems for various uses have been arranged.
Further, in endoscopes used in the industrial field, some endoscope has a zooming function provided in an objective optical system and a function being capable of manually switching between a direct sight and a side sight, what is called as a pan viewing function has been highly required.
When a mechanism for performing a pan viewing function is provided at the distal end of the endoscope for industrial use, not only the endoscope distal end diameter becomes thick but also the structure is complicated. That has become a factor of increasing expenses.
The endoscopes which can perform stereoscopic vision observation shown in Patent Application Laid Open No. 64-26813/1989 and U.S. Pat. No. 5,122,650, and the endoscopes which can perform telephotographic/wide operation shown in Japanese Patent Application Laid Open No. H1-197716/1989 are exclusively used for stereoscopic vision observation or telephotographic/wide operation.
In addition, because the endoscopes form images acquired by two objective optical systems ordinarily use a pair of optical systems for stereoscopic vision observation, the two optical systems have the same f-number (brightness/stop value) and send the common illumination light to both optical systems. In other words, it was not necessary to adjust the quantity of illumination light for each optical system from a light source through a light guide. However, as mentioned above, if an observation image obtained by each objective optical system is formed on the CCD corresponding to each objective optical system and the common quantity of light illuminates two objective optical systems having different magnification in an endoscope performing telephotographic/wide operation by using the common quantity of light, an image having proper brightness for each optical system cannot be obtained, so that it was necessary to adjust and supply the quantity of illumination light being appropriate for each optical system.